Titanium base alloy



Patented May 22, 1951 TITANIUM BASE ALLOY Robert I. Jaffee and Horace R. Ogden, Columbus, Ohio, assig'nors, by mesne assignments, to Remington Arms Company, Inc., Bridgeport, Conn., a corporation of Delaware No Drawing. Application October 20, 1949, Serial No. 122,577

6 Claims. (01. 75134) This invention relates to new and useful titanium base alloys.

This application is a continuation-in-part of our copending application Serial No. 90,776, filed April 30, 1949, now abandoned.

Titanium base alloys generally as known heretofore, in the form of sheets or other mechanically worked shapes, have had only limited utility for structural purposes. They lack the requisite combinations of strength and ductility.

According to this invention, it has been discovered that valuable alloys suitable for such structural purposes can be produced by compounding a titanium base with aluminum and molybdenum so that stable alloy structures composed essentially of the alpha form of titanium together with another distinct microcrystalline phase that probably is the beta form of titanium are obtained.

The presence of the stable second phase in the alloy structure results from incorporating molybdenum as well as aluminum in the titanium base. That phase appears to account for a pronounced increase of strength, accompanied by retained ductility sufficient for mechanical working requirements, which alloys embodying the present invention show as compared with binary titanium-aluminum alloys of similar aluminum content. The latter exhibit a single-phase microstructure composed of the alpha form of titanium.

Alloys possessing desirable combinations of strength, hardness and elastic properties may be obtained according to this invention by incorporating about 2.5 to about 8% of aluminum and ferent physical properties. While strength is high ductility is low. Compositions giving excellent strength and elastic properties result when at least 90% of the whole alloy is titanium and the molybdenum content isbetween about 2 and about 5%. Within these limits which represent preferred embodiments are alloys, for example, which, after being hot rolled and annealed at 850 0., exhibit proportional limits of from 122,000 to 142,000 p. s. i. and ultimate strengths of from 139,000 to 152,000 p. s. i., together with elongations of at least 11% in one inch, and the capacity to undergo cold rolling reductions of to or more without edge cracking.

The titanium base metal used in the present alloys may contain substances or impurities besides titanium, as normally found in either high purity titanium or commercially pure titanium. It may be, for example, a high purity or iodide process titanium as produced according to the Van Arkel United States Patent No. 1,671,213.

Alternatively, it may be a commercial titanium as produced, for example, by magnesium-reduction processes, such as the process of United States Patent No. 2,205,854 to Kroll or modifications thereof; provided that the carbon, oxygen and nitrogen contents of these alloys, hence of the base metal, should not exceed 0.5%, 0.25%

and 0.15%, respectively, nor should they total more than about 0.5%, if the alloys are to possess good ductility as cast or as worked and annealed.

It has been found, however, that the presence of between 0.1 and 0.3% of carbon, with or without about 0.01 to 0.15% each of oxygen or nitrogen or both, is generally quite beneficial. Among the least high-strength alloys of this invention are those made either with a commercial titanium base meeting such specifications, or with a high purity titanium base containing similar amounts of added carbon or added carbon and oxygen, nitrogen, or oxygen and nitrogen. Important embodiments of this invention therefore may be defined as alloys composed essentially of from 2.5 to 7.5% of aluminum and from 0.5 to nearly 10% of molybdenum in a titanium base containing from 0.1 to 0.3% of carbon, or 0.1 to 0.3% of carbon and about 0.01 to 0.15% of oxygen and/or nitrogen.

Illustrative compositions and properties of alloys embodying this invention appear in the following table, which also shows properties of a comparable binary titanium-aluminum alloy:

vacuum annealed for about three hours at about 850 C.

Example 18 of the foregoing table shows that As Hot Rolled and Annealed at 850 0.

Composition Strength Properties 1000 p. s. i.

- Per Cent Per Cent V1ckers Prop. 0.1% 0.2% Ult1- R Hard- Limit Ofiset Ofiset mate Area TI Base A1 Mo ness m 1 daemon High Purity 5 273 44 62 64 78 18 46 l d 1 298 56. 9 81 83. 6 103 51 2 do. 5 2. 5 289 66 83 85 104 12 29 3 d0 5 5 282 61 101 104 117 11 36 4 HP+0.1C 5 2. 5 306 75 103 106 120 16 39 5 HP+0.250 5 2. 5 320 98 121 121 134 18 40 6 HP+0.1N 5 2. 5 314 88 106 108 123 12 41 7 HP+0.2N 5 2. 5 356 107 124 125 138 13 33 8 HP+0.1O2 5 2. 5 307 92 104 108 121 13 40 9 HP+0.2O2 5 2. 5 "333 94 112 114 134 10 10 HP+0.1N+O.10z 5 2. 5 343 110 122 123 138 10 22 ll HP+0.25O|-0.1O2 5 2. 5 363 122 134 136 148 12 12 HP-H).25C+O.202 5 2. 5 386 128 144 148 160 12 18 13 HP+0.250+0.lN 5 2. 5 373 134 137 137 152 8 16 14 HP+O.250+O.lOz+lN 5 2. 5 408 151 159 160 169 4 9 15 HIP-F0250 6 2. 5 351 122 131 133 145 12 29 16 HP+0.25O 7 2. 5 370 139 141 142 152 I2 22 17 HP 7. 5 2. 5 330 123. 6 129. 2 129. 6 141. 3 ll 23 18 Commercial (0.250) 5 2. 5 375 118 8 140 15 33 In addition to desired strength, hardness and ductility properties, the alloys of this invention possess valuable properties of corrosion resistance. Many of them retain a hardness exceeding that of cast commercial titanium, at temperatures as high as 1000 F:, and they can be made with extraordinarily high ratios of strength to weight, since alloys of very high strength can be obtained by using, for example, only about 2.5% of the heavy metal molybdenum with twice as much light aluminum in a titanium base.

The alloys herein disclosed have the second or beta phase in their structure dispersed intergranularly in a matrix of alpha titanium. When they are quenched from 950 C. some increase in hardness results, while quenching them from 1050 C. increases their annealed hardness by about 50 to 80 Vickers points. Aging them after quenching at 400 C. for periods up to 16 hours does not substantially alter their quenched hardness. Alloys containing more than about 10% molybdenum have more finely dispersed phases in their microstructure and respond to heat treatment in a substantially different manner.

The alloys of this invention are preferably prepared by the arc melting of an admixture of their constituents in a comminuted form. Carbon, oxygen or nitrogen may be added, if desired, in the form of solid compounds thereof with titanium. To insure that none of the alloying element is lost, such compounds may be enclosed in a titanium capsule, which is then are melted. Other methods of alloying are, of course, applicable.

Fabrication of the present alloys into sheets is preferably effected by hot rolling. For example, the metal may be heated at a furnace temperature of about 850 0., reduced in thickness about 10% in each pass through rolls, and reheated after each pass. thickness, say 0.04 inch, has been secured, the sheet may be mechanically cleaned and then When the desired an alloy having outstanding properties may be obtained by use of a commercial titanium base containing 0.25% of carbon with 5% of aluminum and 2.5% of molybdenum. The commercial titanium here used showed at 10 kg. Vickers hardness as cast of about 1'70, while the alloy fabricated as above described to a thickness of 0.045 inch, showed a 10 kg. Vickers hardness of about 375. Strips of this alloy could be bent to a {a inch radius without cracking.

What is claimed is:

1. An alloy composed essentially of 2.5 to about 8% of aluminum and 0.5 to about 8% of molybdenum, balance titanium.

2. An alloy composed essentially of 2.5 to about 8% of aluminum and 0.5 to about 8% of molybdenum, balance titanium containing 0.1 to 0.3% of carbon.

3. An alloy composed essentially of 2.5 to 8% of aluminum and 2 to 5% of molybdenum, balance titanium, the titanium content being at least 4. An alloy composed essentially of 2.5 to 8% of aluminum and 2 to 5% of molybdenum, balance titanium containing 0.1 to 0.3% of carbon, the titanium content being at least 90%.

5. An alloy composed essentially of about 5% of aluminum and about 2.5% of molybdenum, balance titanium.

6. An alloy composed essentially of about 5% of aluminum and about 2.5% of molybdenum balance titanium containing about 0.25% of carbon.

ROBERT I. JAFFEE. HORACE R. OGDEN.

REFERENCES CITED The following references are of record in the file of this patent:

FOREIGN PATENTS Number Country Date 718,822 Germany Mar. 24, 1942 

1. AN ALLOY COMPOSED ESSENTIALLY OF 2.5 TO ABOUT 8% OF ALUMINUM AND 0.5 TO ABOUT 8% OF MOLYBDENUM, BALANCE TITANIUM. 